House Extensions · Mullingar & Westmeath
House Extension Architects in Mullingar and Westmeath
Knightwood Architects designs house extensions that add space, light and value to homes across Mullingar, Multyfarnham, Westmeath and the Midlands. We handle the full process: design, planning permission where it is needed, and the drawings your builder needs to price and build the extension properly.
What we design
Extensions we design
Single-storey rear extensions
Two-storey extensions
Kitchen and open-plan living extensions
Side and wraparound extensions
Bedroom and en-suite extensions
Ground-floor bedrooms and accessible living spaces
Extensions combined with a full renovation of the existing house
Planning
Do I need planning permission for an extension in Ireland?
Smaller extensions can be exempted development, meaning no planning permission is needed. Since 27 July 2026, the exemption for extending your main home increased from 40 to 45 square metres, subject to conditions. These include limits on upstairs floor area, distances from boundaries, and keeping enough private garden space at the rear.
If your extension is larger, at the front of the house, affects a protected structure, or breaks any of the conditions, you will need planning permission. We check your project against the current rules at the first consultation and tell you clearly which route applies. Where it is unclear, a Section 5 declaration from the council confirms it in writing.
Costs
How much does a house extension cost in Ireland?
Build costs depend on size, specification, ground conditions and whether you are also altering the existing house. Kitchens, glazing and structural changes have the biggest effect on price. The most reliable way to control cost is a clear design and detailed drawings, so builders can price the same thing and there are fewer extras during construction. We help you set a realistic budget at the start and design to it.
Our process
Our extension design process
Free consultation and site visit — We look at the house, your brief and your budget.
Measured survey — Accurate drawings of the existing house.
Design options — Layouts and 3D views so you can see the space before it is built.
Planning or exemption check — We prepare the planning application, or confirm the extension is exempt.
Building Regulations and construction drawings — Detailed drawings, specifications and, where required, compliance documentation.
Regulations
Building Regulations and certification
Even an exempt extension must comply with the Building Regulations, covering structure, fire safety, ventilation and energy performance. Larger extensions also come under the Building Control (Amendment) Regulations (BCAR), which require a design certifier and an assigned certifier. As registered architects, we can advise on and provide these services.
Questions
Frequently asked questions
How long does a house extension take to design?
Design usually takes 4 to 8 weeks. If planning permission is needed, allow at least 8 weeks for the council’s decision and about 4 more weeks before the final grant.
Can I live in the house during the extension?
Often, yes, for most of the build. We can design the works in phases to reduce disruption, especially where the kitchen is affected.
Will my extension match the existing house?
It can match, or it can contrast in a way that complements the original. Either way, we design it to feel like a natural part of the home.
Start your project
Plan your extension with an architect
Tell us about your home and what you want to add, and we will arrange your free consultation.
Phone: +353 85 178 9380
Email: info@knightwooddesign.com
Related: Planning permission applications · House renovation